Search for stops/stations by name. Returns matches with a naptanId (the "id" field) used by the arrivals tool, plus modes, zone, and lat/lon.
Risk signalsAccepts freeform code/query input (query)
Part of the Tfl server.
Free to start. No card required.
AI agents invoke stop_search to trigger processes or run actions in Tfl. Execute operations can have side effects beyond the immediate call -- triggering builds, sending notifications, or starting workflows. Rate limits and argument validation are essential to prevent runaway execution.
stop_search can trigger processes with real-world consequences. An uncontrolled agent might start dozens of builds, send mass notifications, or kick off expensive compute jobs. PolicyLayer enforces rate limits and validates arguments to keep execution within safe bounds.
Execute tools trigger processes. Rate-limit and validate arguments to prevent unintended side effects.
{
"version": "1",
"default": "deny",
"tools": {
"stop_search": {
"limits": [
{
"counter": "stop_search_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}See the full Tfl policy for all 26 tools.
These attack patterns abuse exactly the kind of access stop_search gives an agent. Each links to the full case and the policy that stops it:
Other execute tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Search for stops/stations by name. Returns matches with a naptanId (the "id" field) used by the arrivals tool, plus modes, zone, and lat/lon.. It is categorised as a Execute tool in the Tfl MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Tfl MCP server in PolicyLayer and add a rule for stop_search: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Tfl. Nothing to install.
stop_search is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the stop_search rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for stop_search. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
stop_search is provided by the Tfl MCP server (https://gateway.pipeworx.io/tfl/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 26 Tfl tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
4,600+ MCP servers and 31,000+ tools scanned and risk-classified.